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 * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.lang;

import java.io.Serializable;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamException;

/**
 * This is the common base class of all Java language enumeration types.
 *
 * More information about enums, including descriptions of the
 * implicitly declared methods synthesized by the compiler, can be
 * found in section 8.9 of
 * <cite>The Java&trade; Language Specification</cite>.
 *
 * <p> Note that when using an enumeration type as the type of a set
 * or as the type of the keys in a map, specialized and efficient
 * {@linkplain java.util.EnumSet set} and {@linkplain
 * java.util.EnumMap map} implementations are available.
 *
 * @param <E> The enum type subclass
 * @author Josh Bloch
 * @author Neal Gafter
 * @see Class#getEnumConstants()
 * @see java.util.EnumSet
 * @see java.util.EnumMap
 * @since 1.5
 */
public abstract class Enum<E extends Enum<E>>
    implements Comparable<E>, Serializable {

  /**
   * The name of this enum constant, as declared in the enum declaration.
   * Most programmers should use the {@link #toString} method rather than
   * accessing this field.
   */
  private final String name;

  /**
   * Returns the name of this enum constant, exactly as declared in its
   * enum declaration.
   *
   * <b>Most programmers should use the {@link #toString} method in
   * preference to this one, as the toString method may return
   * a more user-friendly name.</b>  This method is designed primarily for
   * use in specialized situations where correctness depends on getting the
   * exact name, which will not vary from release to release.
   *
   * @return the name of this enum constant
   */
  public final String name() {
    return name;
  }

  /**
   * The ordinal of this enumeration constant (its position
   * in the enum declaration, where the initial constant is assigned
   * an ordinal of zero).
   *
   * Most programmers will have no use for this field.  It is designed
   * for use by sophisticated enum-based data structures, such as
   * {@link java.util.EnumSet} and {@link java.util.EnumMap}.
   */
  private final int ordinal;

  /**
   * Returns the ordinal of this enumeration constant (its position
   * in its enum declaration, where the initial constant is assigned
   * an ordinal of zero).
   *
   * Most programmers will have no use for this method.  It is
   * designed for use by sophisticated enum-based data structures, such
   * as {@link java.util.EnumSet} and {@link java.util.EnumMap}.
   *
   * @return the ordinal of this enumeration constant
   */
  public final int ordinal() {
    return ordinal;
  }

  /**
   * Sole constructor.  Programmers cannot invoke this constructor.
   * It is for use by code emitted by the compiler in response to
   * enum type declarations.
   *
   * @param name - The name of this enum constant, which is the identifier used to declare it.
   * @param ordinal - The ordinal of this enumeration constant (its position in the enum
   * declaration, where the initial constant is assigned an ordinal of zero).
   */
  protected Enum(String name, int ordinal) {
    this.name = name;
    this.ordinal = ordinal;
  }

  /**
   * Returns the name of this enum constant, as contained in the
   * declaration.  This method may be overridden, though it typically
   * isn't necessary or desirable.  An enum type should override this
   * method when a more "programmer-friendly" string form exists.
   *
   * @return the name of this enum constant
   */
  public String toString() {
    return name;
  }

  /**
   * Returns true if the specified object is equal to this
   * enum constant.
   *
   * @param other the object to be compared for equality with this object.
   * @return true if the specified object is equal to this enum constant.
   */
  public final boolean equals(Object other) {
    return this == other;
  }

  /**
   * Returns a hash code for this enum constant.
   *
   * @return a hash code for this enum constant.
   */
  public final int hashCode() {
    return super.hashCode();
  }

  /**
   * Throws CloneNotSupportedException.  This guarantees that enums
   * are never cloned, which is necessary to preserve their "singleton"
   * status.
   *
   * @return (never returns)
   */
  protected final Object clone() throws CloneNotSupportedException {
    throw new CloneNotSupportedException();
  }

  /**
   * Compares this enum with the specified object for order.  Returns a
   * negative integer, zero, or a positive integer as this object is less
   * than, equal to, or greater than the specified object.
   *
   * Enum constants are only comparable to other enum constants of the
   * same enum type.  The natural order implemented by this
   * method is the order in which the constants are declared.
   */
  public final int compareTo(E o) {
    Enum<?> other = (Enum<?>) o;
    Enum<E> self = this;
    if (self.getClass() != other.getClass() && // optimization
        self.getDeclaringClass() != other.getDeclaringClass()) {
      throw new ClassCastException();
    }
    return self.ordinal - other.ordinal;
  }

  /**
   * Returns the Class object corresponding to this enum constant's
   * enum type.  Two enum constants e1 and  e2 are of the
   * same enum type if and only if
   * e1.getDeclaringClass() == e2.getDeclaringClass().
   * (The value returned by this method may differ from the one returned
   * by the {@link Object#getClass} method for enum constants with
   * constant-specific class bodies.)
   *
   * @return the Class object corresponding to this enum constant's enum type
   */
  @SuppressWarnings("unchecked")
  public final Class<E> getDeclaringClass() {
    Class<?> clazz = getClass();
    Class<?> zuper = clazz.getSuperclass();
    return (zuper == Enum.class) ? (Class<E>) clazz : (Class<E>) zuper;
  }

  /**
   * Returns the enum constant of the specified enum type with the
   * specified name.  The name must match exactly an identifier used
   * to declare an enum constant in this type.  (Extraneous whitespace
   * characters are not permitted.)
   *
   * <p>Note that for a particular enum type {@code T}, the
   * implicitly declared {@code public static T valueOf(String)}
   * method on that enum may be used instead of this method to map
   * from a name to the corresponding enum constant.  All the
   * constants of an enum type can be obtained by calling the
   * implicit {@code public static T[] values()} method of that
   * type.
   *
   * @param <T> The enum type whose constant is to be returned
   * @param enumType the {@code Class} object of the enum type from which to return a constant
   * @param name the name of the constant to return
   * @return the enum constant of the specified enum type with the specified name
   * @throws IllegalArgumentException if the specified enum type has no constant with the specified
   * name, or the specified class object does not represent an enum type
   * @throws NullPointerException if {@code enumType} or {@code name} is null
   * @since 1.5
   */
  public static <T extends Enum<T>> T valueOf(Class<T> enumType,
      String name) {
    T result = enumType.enumConstantDirectory().get(name);
    if (result != null) {
      return result;
    }
    if (name == null) {
      throw new NullPointerException("Name is null");
    }
    throw new IllegalArgumentException(
        "No enum constant " + enumType.getCanonicalName() + "." + name);
  }

  /**
   * enum classes cannot have finalize methods.
   */
  protected final void finalize() {
  }

  /**
   * prevent default deserialization
   */
  private void readObject(ObjectInputStream in) throws IOException,
      ClassNotFoundException {
    throw new InvalidObjectException("can't deserialize enum");
  }

  private void readObjectNoData() throws ObjectStreamException {
    throw new InvalidObjectException("can't deserialize enum");
  }
}
